LBBB 332 and LBBB 362: two unlikely ships go to war
The tragic heritage of Exercise Tiger off Slapton Sands, south Devon, in April 1944 as preparation for the D-Day landings in June that year is well-known: the exercise was disrupted by enemy action, with the loss of Landing Ship Tanks LST-507 and LST-531, both now scheduled monuments. (Learn more in this Historic England article with a contemporary photograph.)
Less well-known off Salcombe, south Devon – perhaps because they were on exercise for an operation which never took place – is a similarly fateful attack on two Landing Barges (Landing Barge Barrage Balloon) LBBB 332 and LBBB 362, on 19 September 1942.
During the spring and summer of 1942, the Allied Powers had been in discussion about undertaking an invasion attempt on France in the forthcoming autumn, codenamed Operation Sledgehammer. Heavily promoted by the Soviet Union and the United States, it was viewed in Britain as having little prospect of success and costly in human and material resources, a view to which the US was also eventually persuaded.  The debacle of the Raid on Dieppe on 19 August 1942 only served to highlight that the Allies were not yet ready to open a second front in Europe, and instead Allied resources were poured into the North African campaign which would lead to victory at El Alamein in November 1942.
However, with Sledgehammer in mind, over the summer of 1942, Britain pressed some apparently rather unlikely vessels into service.  The ‘dumb barges’ of the Thames – so called because they had no propulsion of their own, and could only be towed, or operated with long ‘sweeps’ or oars – would now play their part in the war.
They were requisitioned for repurposing as landing craft, valuable for bringing materials ashore from larger ships, their ‘swim’ ends easily convertible into ramps for offloading, and easily beached because of their shallow draught. [The second photo in this gallery of a contemporary model of a Thames lighter, made around 1940, depicts a sloping flat ‘swim’, rather than pointed or rounded and blunt, end.]
They were then initially fitted with British engines, but were soon re-engined with US-made Chrysler marine engines, supplied under Lend-Lease.  Some of this group were then able to perform exercises under their own power at various locations, with five barges undergoing trials at Salcombe in September 1942.
It would seem that among them were LBBB 332 and LBBB 362, each converted into a Landing Barge Barrage Balloon, amphibious vessels tethering airborne craft. Barrage balloon vessels were not, in themselves, a new idea. From the early days of the war, barrage balloons had been deployed for home defence, compromising the accuracy of enemy aircraft in range-finding and gunnery by forcing them to fly higher. Barrage balloons were thus placed around towns, strategic sites, and, crucially, harbours – anywhere that was a target for air attack.
Those balloons defending ports and harbours were flown from requisitioned barges and other small craft, and several were themselves victims of air attack, among them British drifter Lavinia L, sunk off Sheerness June 1941; and two ex-Belgian fishing vessels in British Admiralty service following the fall of Belgium in 1940, the Borealis, off the Isle of Wight, August 1940, and the Cor Jesu off Alnmouth, August 1941. These losses expose one of the key weaknesses of barrage balloon defence – their very presence signposted sites of importance. (Indeed, the contemporary photograph in Historic England’s aerial photography collections shows barrage balloons off Slapton Sands.)
Other barrage balloon vessels, while guarding against attack from the air, fell victim to the sub-surface wartime dangers of the sea, such as the British drifters Lord St Vincent, mined off Harwich in July 1940, and Carry On, also mined off Sheerness, December 1940. A similar fate befell the tug Lion, again off Sheerness, in January 1941. Her actual role is slightly unclear: she was requisitioned by the Air Ministry for barrage balloon duty but was towing a barge at the time of loss, which might perhaps have been a barrage balloon vessel, given the numbers stationed at Sheerness. 
The vessels at Salcombe and elsewhere represented a development of the need for harbour defence from the air. There were two new elements: one was the idea of an air shield while en route, supplementing conventional air cover, and the other the amphibious component, providing cover forward for the offloading of troops and ammunition on the beach. Salcombe was an ideal test location, since it was one of the existing harbours covered by seaward, but static, barrage balloon defences. 
However, as the other barrage balloon barges sunk elsewhere in the war attest, the barges on exercises became very visible targets for bombing raids. On 19 September 1942, a Luftwaffe air raid took place on Salcombe. It was in that raid that Landing Barges Barrage Balloon LBBB 332 and LBBB 362 were sunk by a Focke-Wulf of 10/JG 26. 
The papers of those involved in the extensive discussions over Operation Sledgehammer laid a documentary trail for something which never, ultimately, took place: the wrecks of the LBBBs form the tangible archaeological counterpart for that documentary trail.
Those wrecks also form a historical bridge between two events which did take place: in their small size and unlikely guise, they were akin to the ‘little ships’ which participated in Operation Dynamo, the evacuation of Dunkirk in 1940; and they were the precursors of the landing barges and the barrage balloon vessels that went in 1944 to the D-Day landing beaches as part of Operation Overlord with both British and American units – the history of the barrage balloon barges has, until recently, has been a crucial, but largely overlooked, heritage in both ships and personnel.  In the same vein, the LBBB wrecks at Salcombe help chart the little-known story of Britain’s preparations for Overlord as early as 1942.
 The National Archives, Churchill Archive, CHAR 20/77/87-90; Matloff, M. & Snell, E (1990) Strategic Planning for Coalition Warfare (Washington DC: Centre of Military History, US Army) 266-292, as published online
 United Kingdom Hydrographic Office 12806
 “Barrage Balloon Vessels”, Barrage Balloon Reunion Club, published online
 Designated as LBBB 332 and LBBB 362 in British Vessels Lost at Sea, 1914-18 and 1939 45 (Yeovil: Patrick Stephens Ltd) (reproduction of HMSO originals), p51; described as ‘dumb barges of 150-ton type’ in Smith Part 2; Brine, M nd “Casualties of the Bombing at Salcombe”, Devon Heritage (published online); Goss, C, Cornwell, P, and Rauchbach, B, 2003 Luftwaffe Fighter-Bombers over Britain: The Tip and Run Campaign 1942-3 (Manchester: Crécy Publishing Ltd.)
 Hervieux, L 2015 “How Black Barrage Balloon Troops Kept the D-Day Beaches Safe”, Military History Now, published online; Military Health Systems Communications Office, 2022 “This D-Day veteran hit the beach strapped to a barrage balloon”, We Are The Mighty, published online